Microservice test strategy

Unit, Integration, Component, and Contract tests should be written by developers
E2E tests should be written by Automation test engineers
Developers should support Automation test engineers with tools for mocking and test data setup

Unit tests

Developers should write unit tests for every newly added class
Developers should write tests for existing classes, covering only newly added logic
All interactions and collaborations between an object and its dependencies, should be replaced by test doubles (Solitary unit testing)
Using code coverage extension FineCodeCoverage in Visual studio to validate coverage
Unit tests should be part of the story
If unit tests are not possible to write because of business pressure, a tech dept task should be created with a list of classes that don't cover with tests, PM should notified that tests should be written after releases as first priority

What to cover

Cover everything that is possible with unit tests

Classes with business logic
Controllers
Attributes
Model Validators
Filters
etc ..

When to run

Run manually by developers locally using Fine code coverage extension
Run in PR before the merge, all tests should pass
Measure code coverage using Visual studio test task
Setup baseline for test coverage and revision condition each month

Integration tests (test-only integration)

Developers should write integration tests for every newly added repository class
Developers should write integration tests for existing classes, covering only newly added logic
Setup test data using SQL or EF queries
Each test should set and clean test data
Tests should support running in parallel

What to cover

Repositories
HTTP Clients
Tests should test database migrations, before merge to main branch

When to run

Integration tests should run in PR gate before the merge

Database test double

Make a backup of the latest copy of the database and remove redundant data
Run database in docker container using tmpfs (in memory storage)
Before starting an integration test run docker inside test using docker client and stop it after

Component tests

In-process component tests

In a microservices architecture, a component can be a single microservice itself.

Developers should mock all external dependencies like Database, External API using in memory mocks.

Test Doubles & test run framework

Run tests using Microsoft Test server integration testing framework.
Use in-memory Entity framework for database
Use Moq for other dependencies

What to cover

Test request validations and Authentication attributes

Developers should mock everything inside the controller
Developers should cover authorization attributes and claims
Developers should cover model validation and binding

Test business logic with in-memory mocks

Write tests for each controller that tests business logic.

When to run

should run in PR gate pipeline

E2E tests (integrations+configurations testing)

Test that the application started and run

Test database health check
Test External system HttpClient (call health checks)
Run a simple smoke test for the main flow in the microservice

Resources

microservice-testing